It is generally known that L-ascorbic acid (vitamin C) has, besides the function of inhibiting lipid peroxides, the functions of promoting the production of collagen and strengthening the immune system, the functions of inhibiting the synthesis of melanin under the skin and reducing and fading any black melanin that has been synthesized. Thus, L-ascorbic acid is a well-known component of skin-whitening cosmetics that can inhibit the synthesis and/or reduce synthesized melanin, thereby inhibiting “spots” and “freckles”.
L-ascorbic acid is extremely unstable to heat or oxidation and tend to become inert or decompose when heated or oxidized. This may make it difficult for L-ascorbic acid to fully exhibit its expected physiological function.
In order to prevent L-ascorbic acid from becoming unstable, there are known a derivative in which the diol portion of L-ascorbic acid, which is prone to oxidation, is subjected to phosphate esterification (Patent publication 1), and a derivative in which the diol portion is subjected to glycosidation (Patent publication 2).
But because these L-ascorbic acid derivatives are high in hydrophilicity, they are low in permeability into the skin.
In order to improve permeability of L-ascorbic acid into the skin, there are known an L-ascorbic acid derivative in which position 6 of L-ascorbic acid is acylated (Patent document 3), and a derivative in which position 4 of L-ascorbic acid is acylated (Patent document 4).
An L-ascorbic acid derivative is also known which shows both superior stability and permeability into the skin by acylating position 6 of L-ascorbic acid and further subjecting position 2 to phosphate esterification (Patent publication 5).    Patent document 1: JP patent publication 52-18191B    Patent document 2: JP patent publication 03-139288A    Patent document 3: JP patent publication 59-170085A    Patent document 4: JP patent publication 45-23634B    Patent document 5: JP patent publication 10-298174A